Telescopic sights have a lead mark, for example in the form of a reticle. In order to be able to adjust the lead mark to the actual point of impact for specific ballistics (caliber, projectile mass, type of projectile, charge, etc.) and a specific barrel for a specific zero range, the lead mark is usually adjustable for elevation and deflection in known manner by means of an adjusting mechanism.
In addition, different construction designs have been disclosed that make it possible to index the adjusted position by means of an index mark (zeroing).
With such designs, however, it is usually only possible to index one specific setting, ie only one zero mark, for the point of impact for specific ballistics using a specific barrel for just one shooting range.
An actuator of the type described at the outset for use on a telescopic sight and enabling multiple zeroing, ie zeroing for a number of ranges and/or for different ballistics and/or different gun barrels etc., is disclosed, for example, by Leatherwood (USA) under the name of “Uni-Dial” (see also US 2004/0144013 A1). This actuator exhibits a number of indicator flags that can be rotated in the actuator. The actuator is embodied in the form of a rotary knob that consists of several disk-shaped elements positioned around the axis of rotation of the unit. The flags are disposed on flat disks located between the disk-shaped elements of the rotary knob (turret) (in the disclosed embodiment the disk-shaped elements of the rotary knob are substantially thicker than the disks having the flags) and are displaceable in an adjustment mode of the actuator, ie the disks on which the flags are located can be rotated about the axis of rotation without the lead mark itself being displaced.
In the operating mode, after zeroing for different shooting ranges, barrels, etc., the flags are fixed in their adjusted position by screwing, or otherwise fixing, the rotary knob (ie the plates that form the rotary knob) such that the said plates are pressed tightly against each other so that the flag indicator plates are squeezed between the disks of the rotary knob and are entrained with the knob when the latter is rotated.
The disadvantage of this system, however, is that in order to adjust the individual flags, the rotary knob must be “loosened”, ie its clamping action must be released such that the turret plates become slightly displaceable along the axis of rotation and the flags, or rather the plates carrying the flags, become rotatable. However, for this purpose, the tower must be slackened in a separate procedure, on the one hand, and, on the other hand, this leads—in a particularly detrimental manner—to all flags becoming loose so that flags that have already been adjusted can be easily accidentally moved from their settings.